Block-based audio encoding/decoding device and method therefor

ABSTRACT

Provided is an apparatus and method for encoding/decoding audio based on a block. A method of encoding an audio signal may include dividing each of frame of input signal that constitute an audio signal into a plurality of subframes; transforming the subframes to a frequency domain; determining a two-dimensional (2D) intra block using the subframes transformed to the frequency domain; and encoding the 2D intra block. The 2D intra block may be a block that two-dimensionally displays frequency coefficients of the subframes transformed to the frequency domain using a time and a frequency.

TECHNICAL FIELD

At least one example embodiment relates to an apparatus and method forencoding/decoding an audio signal.

RELATED ART

Technology for encoding/decoding an audio signal refers to technologyfor compressing an audio signal and transmitting the compressed audiosignal. The great technical developments have been achieved over thepast decades.

1st generation (1G) MPEG audio encoding/decoding technology, that is,MPEG-1 layer III (MP3) technology refers to a scheme of designing aquantizer and compressing data based on a psychoacoustic model of ahuman being to minimize a loss of a perceptual sound quality.

2nd generation (2G) MPEG audio encoding/decoding technology, that is,MPEG-2 advanced audio coding (AAC) technology refers to a scheme ofenhancing a compression performance by applying a psychoacoustic modelto a full band audio frequency coefficient based on modified discretecosine transform (MDCT).

3rd generation (3G) MPEG audio encoding/decoding technology, that is,MPEG-4 parametric coding technology refers to a scheme of enhancing acompression rate from a low bitrate of 48 kbps or less using parametriccoding technology. For example, the parametric encoding/decodingtechnology includes parametric stereo (PS) technology forencoding/decoding a stereo channel and spectral band replication (SBR)technology for encoding/decoding a high band signal.

4th generation (4G) MPEG audio encoding/decoding technology, that is,unified speech and audio coding (USAC) technology refers to USAC audiocodec technology for enhancing the sound quality of low bitrate voice,and has a compression performance similar to AAC 128 kbps to provide aCD-class high quality.

That is, the audio encoding/decoding technologies according to therelated art may be understood to enhance the compression performanceusing the psychoacoustic model, however, to reach the limit ofperformance due to a quantization based on a one-dimensional (1D)psychoacoustic model.

Accordingly, there is a need for a method of enhancing an encoding rateby encoding/decoding an audio signal using another method instead ofapplying a 1D psychoacoustic model.

DESCRIPTION Subject

At least one example embodiment provides an apparatus and method thatmay enhance an encoding rate by reconfiguring and encoding an inputaudio signal as a two-dimensional (2D) signal.

Also, at least one example embodiment provides an apparatus and methodthat may flexibly perform homogeneity and synchronization of an encodingscheme since the same framing structure as a video signal may beachieved using an encoding scheme that is interpreted based on a blockunit.

Solution

According to an example embodiment, there is provided a method ofencoding an audio signal, the method including dividing each of frame ofinput signal that constitute an audio signal into a plurality ofsubframes; transforming the subframes to a frequency domain; determininga two-dimensional (2D) intra block using the subframes transformed tothe frequency domain; and encoding the 2D intra block. The 2D intrablock is a block that two-dimensionally displays frequency coefficientsof the subframes transformed to the frequency domain using a time and afrequency.

The transforming of the subframes to the frequency domain may includegrouping the subframes based on an overlap-add; applying a window to thegrouped subframes; and transforming the subframes to which the window isapplied to the frequency domain.

The grouping may include grouping a last subframe divided from a currentframe and a first subframe divided from a subsequent frame among theframe of input signal.

The encoding may include dividing each of the subframes of the 2D intrablock into a plurality of subband signals; predicting a correlationbetween the subband signals; quantizing a high band signal of which abandwidth value is greater than a reference value among the subbandsignals, using a scale factor; quantizing a prediction result of a lowband signal of which a bandwidth value is less than or equal to thereference value among the subband signals and a residual signal betweenthe subband signals; and converting a quantization index, the scalefactor, the quantized high band signal, the residual signal, and theprediction result to a bitstream.

According to an example embodiment, there is provided a method ofdecoding an audio signal, the method including decoding atwo-dimensional (2D) intra block from a received bitstream; determiningsubframes of a frequency domain using the 2D intra block; transformingthe subframes of the frequency domain to subframes of a time domain;determining frame of input signal by performing an overlap-add processon the subframes of the time domain; and decoding the audio signal usingthe frame of input signal.

According to an example embodiment, there is provided a method ofencoding an audio signal, the method including grouping frame of inputsignal that constitute an audio signal based on an overlap-add; applyinga window to the grouped frame of input signal; transforming the frame ofinput signal to which the window is applied to a frequency domain;determining a 2D inter block using the frame of input signal transformedto the frequency domain; and encoding the 2D inter block. The 2D interblock is a block that two-dimensionally displays frequency coefficientsof the frame of input signal transformed to the frequency domain using atime and a frequency.

The encoding may include dividing each of the frame of input signal ofthe 2D inter block into subband signals; predicting a correlationbetween the subband signals; quantizing each of the subband signals; andcalculating a prediction gain based on the correlation and quantizing aresidual signal between the subband signals.

According to an example embodiment, there is provided a method ofdecoding an audio signal, the method including decoding a 2D inter blockfrom a received bitstream; determining frame of input signal of afrequency domain using the 2D inter block; transforming the frame ofinput signal of the frequency domain to frame of input signal of a timedomain; and decoding an audio signal that includes the frame of inputsignal by performing an overlap-add process on the subframes of the timedomain.

According to an example embodiment, there is provided a method ofencoding an audio signal, the method including determining a 2D interblock using first frame of input signal that constitute an audio signal;encoding the 2D inter block; restoring second frame of input signal fromthe encoded 2D inter block; determining a 2D intra block using aresidual signal between the second frame of input signal and the firstframe of input signal; encoding the 2D intra block; and mixing theencoded 2D inter block and the encoded 2D intra block.

The determining of the 2D inter block may include grouping a pluralityof first frame of input signal based on an overlap-add; applying awindow to the grouped first frame of input signal; transforming thefirst frame of input signal to which the window is applied to afrequency domain; and determining a 2D inter block using the first frameof input signal transformed to the frequency domain.

The determining of the 2D intra block may include dividing the residualsignal between the second frame of input signal and the first frame ofinput signal into a plurality of subframes; transforming the subframesto a frequency domain; and determining a 2D intra block using thesubframes transformed to the frequency domain.

According to an example embodiment, there is provided a method ofdecoding an audio signal, the method including decoding a 2D inter blockfrom an encoded 2D inter block; restoring groups of an frame of inputsignal from the 2D inter block; determining a second frame of inputsignal by performing an overlap-add process on the restored groups offrame of input signal; decoding a 2D intra block from an encoded 2Dintra block; restoring a residual signal from the 2D intra block; andrestoring a first frame of input signal that is an original frame ofinput signal using the residual signal and the second frame of inputsignal.

According to an example embodiment, there is provided a method ofencoding an audio signal, the method including determining 2D intrablocks by dividing each of first frame of input signal that constitutean audio signal into a plurality of first subframes; encoding the 2Dintra blocks; restoring second subframes from the encoded 2D intrablocks; determining second frame of input signal by combining the secondsubframes; determining a 2D inter block using residual signals betweenthe second frame of input signal and the first frame of input signal;encoding the 2D inter block; and mixing the encoded 2D inter block andthe encoded 2D intra block.

The encoding of the 2D inter block may include setting first subframesof the 2D intra blocks as a macro block; predicting a correlationbetween macro blocks; performing a differential pulse code modulation(DPCM) to macro blocks corresponding to a highest predicted correlation;quantizing each of the macro blocks; and calculating a prediction gainbased on a result of the DPCM, and quantizing a residual signal betweenthe macro blocks corresponding to the highest correlation.

According to an example embodiment, there is provided a method ofdecoding an audio signal, the method including decoding a 2D inter blockfrom an encoded 2D inter block; restoring groups of frames of a residualsignal from the 2D inter block; determining the residual signal byperforming an overlap-add process on the groups of the frames of theresidual signal; decoding a 2D intra block from an encoded 2D intrablock; determining a second frame of input signal from the 2D intrablock; and restoring a first frame of input signal that is an originalframe of input signal using the second frame of input signal and theresidual signal.

The determining of the second frame of input signal may includedetermining subframes of a frequency domain using the 2D intra block;transforming the subframes of the frequency domain to subframes of atime domain; and determining a second frame of input signal byperforming an overlap-add process on the subframes of the time domain.

According to an example embodiment, there is provided a method ofencoding an audio signal, the method including determining 2D intrablocks by dividing each of frame of input signal that constitute anaudio signal into a plurality of subframes; determining a 2D inter blockusing residual signals between the 2D intra blocks and encoded 2D intrablocks; encoding the 2D inter block; and mixing the 2D inter block andthe 2D intra block.

According to an example embodiment, there is provided a method ofdecoding an audio signal, the method including decoding a 2D inter blockfrom an encoded 2D inter block; restoring groups of frames of a residualsignal from the 2D inter block; restoring the residual signal byperforming an overlap-add process on the groups of the frames of theresidual signal; restoring a before-encoding 2D intra block using anencoded 2D intra block and the residual signal; and restoring the audiosignal using the before-encoding 2D intra block.

The restoring of the groups of the frames of the residual signal mayinclude determining frames of a frequency domain using the 2D interblock; transforming the frames of the frequency domain to frames of atime domain; and restoring groups of frames that constitute the residualsignal by releasing a window from the frames of the time domain.

Effect

According to example embodiments, it is possible to enhance an encodingrate by reconfiguring and encoding an input audio signal as atwo-dimensional (2D) signal.

Also, according to example embodiments, since the same framing structureas a video signal may be achieved using an encoding scheme that isinterpreted based on a block unit, it is possible to flexibly performhomogeneity and synchronization of an encoding scheme compared to aconventional encoding method.

DETAILED DESCRIPTION OF DRAWINGS

FIG. 1 is a diagram illustrating an audio encoding apparatus and anaudio decoding apparatus according to an example embodiment.

FIG. 2 is a flowchart illustrating a method of encoding an audio signalaccording to a first example embodiment.

FIG. 3 illustrates an example of an audio encoding process according tothe first example embodiment.

FIG. 4 illustrates an example of a quantization method according to thefirst example embodiment.

FIG. 5 is a flowchart illustrating an audio decoding method according tothe first example embodiment.

FIG. 6 illustrates an example of an audio decoding process according tothe first example embodiment.

FIG. 7 is a flowchart illustrating a method of encoding an audio signalaccording to a second example embodiment.

FIG. 8 illustrates an example of an audio encoding process according tothe second example embodiment.

FIG. 9 illustrates an example of a quantization method according to thesecond example embodiment.

FIG. 10 is a flowchart illustrating an audio decoding method accordingto the second example embodiment.

FIG. 11 illustrates an example of an audio decoding process according tothe second example embodiment.

FIG. 12 is a flowchart illustrating a method of encoding an audio signalaccording to a third example embodiment.

FIG. 13 illustrates an example of an audio encoding process according tothe third example embodiment.

FIG. 14 is a flowchart illustrating an audio decoding method accordingto the third example embodiment.

FIG. 15 illustrates an example of an audio decoding process according tothe third example embodiment.

FIG. 16 is a flowchart illustrating a method of encoding an audio signalaccording to a fourth example embodiment.

FIG. 17 illustrates an example of an audio encoding process according tothe fourth example embodiment.

FIG. 18 is a flowchart illustrating an audio decoding method accordingto the fourth example embodiment.

FIG. 19 illustrates an example of an audio decoding process according tothe fourth example embodiment.

FIG. 20 is a flowchart illustrating a method of encoding an audio signalaccording to a fifth example embodiment.

FIG. 21 illustrates an example of an audio encoding process according tothe fifth example embodiment.

FIG. 22 illustrates an example of a quantization method according to thefifth example embodiment.

FIG. 23 is a flowchart illustrating a method of an audio decoding methodaccording to the fifth example embodiment.

FIG. 24 illustrates an example of an audio decoding process according tothe fifth example embodiment.

BEST MODE

Hereinafter, example embodiments are described in detail with referenceto the accompanying drawings. A method of encoding an audio signalaccording to an example embodiment may be performed by an audio encodingapparatus. Also, an audio decoding method according to an exampleembodiment may be performed by an audio decoding apparatus.

FIG. 1 is a diagram illustrating an audio encoding apparatus and anaudio decoding apparatus according to an example embodiment.

Referring to FIG. 1, an audio encoding apparatus 100 may include anencoding block 111 and a transmitter 112.

The encoding block 111 may reconfigure an input audio signal as atwo-dimensional (2D) signal. The encoding block 111 may encode the inputaudio signal that is reconfigured as the 2D signal and may output abitstream.

Here, the encoding block 111 may generate an intra block that is a 2Dsignal based on an intra block encoding scheme of determining as a blockand quantizing at least one of audio frames that constitute the inputaudio signal, and may encode the intra block. An encoding operationbased on the intra block encoding scheme is described with reference toFIGS. 2 through 4.

Also, the encoding block 111 may generate an inter block that is a 2Dsignal based on an inter block encoding scheme of determining as a blockand quantizing audio frames that constitute the input audio signal, andmay encode the inter block. An encoding operation based on the interblock encoding scheme is described with reference to FIGS. 7 and 8.

The encoding block 111 may encode the input audio signal using all ofthe inter block encoding scheme and the intra block encoding scheme.

For example, the encoding block 110 may encode the input audio signalbased on the inter block encoding scheme, and may encode a residualsignal between the encoded audio signal and a restored audio signalbased on the intra block encoding scheme. An operation of applying theinter block encoding scheme and then performing encoding based on theintra block encoding scheme is described with reference to FIGS. 12 and13.

As another example, the encoding block 110 may encode the input audiosignal based on the intra block encoding scheme and may encode adifferential signal between a restored audio signal that is restoredfrom the encoded audio signal and an original audio signal based on theinter block encoding scheme. An operation of applying the intra blockencoding scheme and then performing encoding based on the inter blockencoding scheme is described with reference to FIGS. 16 and 17.

As another example, the encoding block 110 may encode the input audiosignal based on the intra block encoding scheme and may encode adifferential signal between the encoded audio signal and an originalaudio signal based on the inter block encoding scheme. An operation ofapplying the intra block encoding scheme and then encoding thedifferential signal between the encoded audio signal and the originalaudio signal based on the inter block encoding scheme is described withreference to FIGS. 20 through 22.

The transmitter 112 may transmit the bitstream output from the encodingblock 111 to an audio decoding apparatus 120.

The audio decoding apparatus 120 may decode and output the audio signalfrom the bitstream that is received from the audio encoding apparatus110.

A receiver 121 may receive the bitstream from the transmitter 112, andmay transfer the bitstream to a decoding block 122. Here, the bitstreamreceived by the receiver 121 may be an inter block bitstream, an intrablock bitstream, or a bitstream in which the intra block bitstream andthe inter block bitstream are mixed.

The decoding block 122 may decode an output audio signal correspondingto the input audio signal from the bitstream.

Here, when the encoding block 111 performs encoding based on the intrablock encoding scheme, the decoding block 122 may synthesize an originalintra frame based on an overlap-add and may decode the output audiosignal from the original intra frame. An operation of decoding theencoded bitstream based on the intra block encoding scheme is describedwith reference to FIGS. 5 and 6.

Also, when the encoding block 111 performs encoding based on the interblock encoding scheme, the decoding block 122 may restore frame of inputsignal using an inter block, may overlap-add the frame of input signal,and may decode the output audio signal. An operation of decoding theencoded bitstream based on the inter block encoding scheme is describedwith reference to FIGS. 10 and 11.

When the encoding block 111 encodes the input audio signal using all ofthe inter block encoding scheme and the intra block encoding scheme, thedecoding block 122 may decode and combine an inter block bitstream andan intra block bitstream, and may decode the output audio signal. Anoperation of decoding, by the encoding block 111, the encoded bitstreamusing all of the inter block encoding scheme and the intra blockencoding scheme is described with reference to FIGS. 14, 15, 18, 19, 23,and 24.

Since the audio encoding apparatus 110 reconfigures and encodes theinput audio signal as the 2D signal, an encoding efficiency may beenhanced. Also, since the audio encoding apparatus 110 may achieve thesame framing structure as a video signal using an encoding scheme thatis interpreted based on a block unit, homogeneity and synchronization ofthe encoding scheme may be flexibly performed compared to an encodingmethod according to the related art.

FIG. 2 is a flowchart illustrating a method of encoding an audio signalaccording to a first example embodiment.

In operation 210, the encoding block 111 may split each of frame ofinput signal that constitute an audio signal into a plurality ofsubframes.

In operation 220, the encoding block 111 may transform the subframessplit in operation 210 to a frequency domain.

Here, the encoding block 111 may group the subframes based on anoverlap-add.

The encoding block 111 may apply a window to the grouped subframes. Theencoding block 111 may transform the subframes to which the window isapplied to the frequency domain.

Here, the encoding block 111 may group a last subframe divided from acurrent frame and a first subframe divided from a subsequent frame amongcurrently processing frame of input signal.

In operation 230, the encoding block 111 may generate a 2D intra blockusing the subframes that is transformed to the frequency domain inoperation 220.

Here, the 2D intra block may be a block that two-dimensionally displaysthe frame of input signal in the frequency domain. For example, the 2Dintra block may be a block that two-dimensionally displays the frequencycoefficients of the subframes transformed to the frequency domain usinga time and a frequency.

In operation 240, the encoding block 111 may encode the 2D intra blockgenerated in operation 230. Here, the encoding block 111 may split eachof the subframes of the 2D intra block into a plurality of subbandsignals. The encoding block 111 may predict a correlation between thesubband signals.

The encoding block 111 may quantize a high band signal of which abandwidth value is greater than or equal to a reference value among thesubband signals using a scale factor. Also, the encoding block 111 mayquantize a prediction result of a low band signal of which a bandwidthvalue is less than or equal to the reference value among the subbandsignals and a residual signal between the subband signals.

The encoding block 111 may convert a quantization index, the scalefactor, the quantized high band signal, the residual signal, and theprediction result to a bitstream.

FIG. 3 illustrates an example of an audio encoding process according tothe first example embodiment.

In FIG. 3, a signal indicated with/hatching may be an audio signal of atime domain and a signal indicated with \ hatching may be an audiosignal of a frequency domain.

Referring to FIG. 3, an input audio signal 300 may include a pluralityof frame of input signal 301. Here, an frame of input signal may be aone-dimensional (1D) audio frame. For example, the frame of input signalmay be an intra frame.

The encoding block 111 may split the frame of input signal 310 into aplurality of subframe 302 using a splitter 310.

The encoding block 111 may group the subframes 302 based on anoverlap-add. For example, the encoding block 111 may group the subframes302 by two based on 50% overlap-add to perform an overlap-add process onthe subframes 302. In detail, the encoding block 111 may group a firstsubframe 1 and a second subframe 2 of a current frame among the frame ofinput signal. Next, the encoding block 111 may group the second subframe2 and a third subframe 3 of the current frame among the frame of inputsignal. That is, the encoding block 111 may group subframes so that aportion of subframes included in a group may be overlap-addpinglyincluded in another group.

Also, the encoding block 111 may group b that is a last subframe of thecurrent frame and b+1 that is a first frame of a subsequent frame forconnection between the current frame and the subsequent frame among theframe of input signal.

The encoding block 111 may apply a window to the grouped subframes. Forexample, the encoding block 111 may apply a sine window or a KaiserBessel window to the grouped subframes.

The encoding block 111 may transform the subframes to which the windowis applied to a frequency domain. Here, the encoding block 111 maytransform the subframes to the frequency domain by applying a modifieddiscrete cosine transform (MDCT) to the subframes to which the window isapplied based on 50% overlap-add.

The encoding block 111 may input the subframes 320 transformed to thefrequency domain to an integrator 320, and may generate a 2D intra block303.

For example, when a number of frequency coefficients of the subframes320 transformed to the frequency domain is N, a time axis resolution isW, and a frequency resolution is H, the 2D intra block 303 may berepresented by N=W×H. Here, W denotes a width of the 2D intra block 303and H denotes a height of the 2D intra block 303.

The encoding block 111 may quantize a single 2D intra block 303 insteadof quantizing each of the subframes. Thus, it is possible to enhance anencoding efficiency compared to a scheme of independently quantizing thesubframes.

Here, the encoding block 111 may perform quantization by predicting acorrelation between the subframes 302 from the 2D intra block 303 and byminimizing an amount of information of the 2D intra block 303. A methodof quantizing the 2D intra block 303 is described with reference to FIG.4.

The encoding block 111 may perform entropy encoding/decoding on thequantization index and related information using an encoder 330, and mayoutput a bitstream.

FIG. 4 illustrates an example of a quantization method according to thefirst example embodiment.

The encoding block 111 may split each of subframes of a 2D intra blockinto a plurality of subband signals. For example, referring to FIG. 4, asubframe 1 of the 2D intra block may be split into subband xf(0,1) tosubband xf(k,1). Here, an index k denotes a number of subbands.

The encoding block 111 may predict a correlation between subbandsignals. For example, the encoding block 111 may perform a primaryprediction using a differential pulse code modulation (DPCM) scheme ormay perform a high-order prediction using a linear predictioncoefficient (LPC) scheme.

The encoding block 111 may perform a coarse quantization on a high bandsignal of which a bandwidth value is greater than a reference valueamong the subband signals, using a scale factor. For example, thereference value may be 4 kHz.

Also, the encoding block 111 may quantize a prediction result of a lowband signal of which a bandwidth value is less than or equal to thereference value among the subband signals and a residual signal betweenthe subband signals. Here, the encoding block 111 may perform conversionto the bitstream by applying a lossless compression process to a numberof quantized low band predictions and the residual signal.

The encoding block 111 may convert the quantization index to thebitstream using a lossless compression scheme, for example, an entropycoding scheme. Also, the quantization index may be converted to thebitstream by quantizing the scale factor separate from the quantizationapplied to the high band signal and the quantization index and byperforming the lossless compression process.

FIG. 5 is a flowchart illustrating an audio decoding method according tothe first example embodiment.

In operation 510, the decoding block 122 may decode a 2D intra blockfrom a bitstream received by the receiver 121.

In operation 520, the decoding block 122 may generate subframes of afrequency domain using the 2D intra block decoded in operation 510.

In operation 530, the decoding block 122 may transform the subframes ofthe frequency domain generated in operation 520 to subframes of a timedomain.

In operation 540, the decoding block 122 may generate an frame of inputsignal by performing an overlap-add process on the subframes of the timedomain transformed in operation 520.

Here, the decoding block 122 may restore grouped subframes by releasinga window from the subframes of the time domain. The decoding block 122may perform the overlap-add process on the subframes included in thegroup.

Also, the decoding block 122 may decode an output audio signal usingframe of input signal.

FIG. 6 illustrates an example of an audio decoding process according tothe first example embodiment.

The decoding block 122 may decode a 2D intra block 602 from a bitstream601 using a decoder 610.

The decoding block 122 may split the 2D intra block 602 using a splitter620, and may generate subframes 603 of a frequency domain.

The decoding block 122 may transform the subframes of the frequencydomain to subframes of a time domain. Here, the decoding block 122 mayrestore grouped subframes 604 by releasing a window from the subframesof the time domain. The decoding block 122 may perform an overlap-addprocess on subframes included in a group using an overlap-addper 630.For example, the decoding block 122 may generate an frame of inputsignal 605 that includes subframe 1, subframe 2, and subframe 3 byperforming an overlap-add process on a group that includes the subframe1 and the subframe 2 and a group that includes the subframe 2 and thesubframe 3.

Here, b+1 that is a first frame of a subsequent frame grouped with bthat is a last frame of a current frame may be overlap-addpingly addedto a first group of the subsequent frame. In detail, a last group (b,b+1) of the current frame may be overlap-addpingly added to a firstgroup (b+1, b+2) of the subsequent frame.

Referring to FIG. 6, the decoding block 122 may decode an output audiosignal 600 that includes the frame of input signal 605 by sequentiallydetermining the frame of input signal 605 through iteration of theaforementioned processes.

FIG. 7 is a flowchart illustrating a method of encoding an audio signalaccording to a second example embodiment.

In operation 710, the encoding block 111 may group frame of input signalthat constitute an audio signal based on an overlap-add. Here, theencoding block 111 may group the frame of input signal by two based on50% overlap-add to perform an overlap-add process on the frame of inputsignal.

In operation 720, the encoding block 111 may apply a window to the frameof input signal grouped in operation 710.

In operation 730, the encoding block 111 may transform the frame ofinput signal to which the window is applied in operation 720 to afrequency domain. Here, the encoding block 111 may transform the frameof input signal to the frequency domain by applying an MDCT to the frameof input signal to which the window is applied based on 50% overlap-add.

In operation 740, the encoding block 111 may generate a 2D inter blockusing the frame of input signal transformed to the frequency domain inoperation 730. Here, the 2D inter block may be a block thattwo-dimensionally displays frequency coefficients of the frame of inputsignal transformed to the frequency using a time and a frequency.

In operation 750, the encoding block 111 may encode the 2D inter blockgenerated in operation 740.

Here, the encoding block 111 may split each of the frame of input signalof the 2D inter block into subband signals. The encoding block 111 maypredict a correlation between the subband signals. The encoding block111 may quantize each of the subband signals. The encoding block 111 maycalculate a prediction gain based on the correlation and may quantize aresidual signal between the subband signals.

FIG. 8 illustrates an example of an audio encoding process according tothe second example embodiment.

In FIG. 8, a signal indicated with/hatching may be an audio signal of atime domain and a signal indicated with \ hatching may be an audiosignal of a frequency domain.

Referring to FIG. 8, an input audio signal may include a plurality offrame of input signal 801.

The encoding block 111 may generate groups 802 by grouping frame ofinput signal that constitute an audio signal by two or more based on anoverlap-add. Here, the encoding block 111 may group the frame of inputsignal by two based on 50% overlap-add to perform an overlap-add processon the frame of input signal.

The encoding block 111 may apply a window to the groups 802. Forexample, the encoding block 111 may apply a sine window or a KaiserBessel window to the groups 802.

The encoding block 111 may transform the frame of input signal to whichthe window is applied, from a time domain to the frequency domain. Here,the encoding block 111 may transform the frame of input signal to thefrequency domain by applying an MDCT to the frame of input signal towhich the window is applied based on 50% overlap-add.

The encoding block 111 may input frame of input signal 803 transformedto the frequency domain to an integrator 810, and may generate a 2Dinter block 804. Here, the 2D inter block may be a block thattwo-dimensionally displays frequency coefficients of the frame of inputsignal transformed to the frequency domain using a time and a frequency.

The encoding block 111 may quantize a single 2D inter block 804 insteadof quantizing each of the frame of input signal 801. Thus, it ispossible to enhance an encoding efficiency compared to a scheme ofindependently quantizing the frame of input signal 801.

Here, the encoding block 111 may perform quantization by predicting acorrelation between the frame of input signal 801 from the 2D interblock 804 and by minimizing an amount of information of the 2D interblock 804. A method of quantizing the 2D inter block 804 is describedwith reference to FIG. 9.

The encoding block 111 may perform entropy encoding/decoding on aquantization index and related information using an encoder 330, and mayoutput a bitstream.

FIG. 9 illustrates an example of a quantization method according to thesecond example embodiment.

The encoding block 111 may split each of frame of input signal of a 2Dinter block into subband signals. For example, referring to FIG. 9, anframe of input signal (Frame 0) of the 2D inter block may be split intosubband sf(0, 0) to subband sf(N/2, 0). Here, N denotes a number offrequency coefficients.

The encoding block 111 may quantize each of the subband signals. Here,the encoding block 111 may predict a correlation between the subbandsignals.

The encoding block 111 may calculate a prediction gain based on thecorrelation and may quantize a residual signal between the subbandsignals. Here, the encoding block 111 may calculate the prediction gainusing a DPCM scheme and an LPC scheme.

The encoding block 111 may perform quantization by applying a scalefactor to the residual signal and may perform lossless compression.

FIG. 10 is a flowchart illustrating an audio decoding method accordingto the second example embodiment.

In operation 1010, the decoding block 122 may decode a 2D inter blockfrom a bitstream received by the receiver 121.

In operation 1020, the decoding block 122 may decode frame of inputsignal of a frequency domain using the 2D inter block decoded inoperation 1010.

In operation 1030, the decoding block 122 may transform the frame ofinput signal of the frequency domain decoded in operation 1020 to frameof input signal of a time domain. Here, the decoding block 122 mayrestore groups of frame of input signal by releasing a window from theframe of input signal of the time domain.

In operation 1040, the decoding block 122 may decode an original frameof input signal that constitutes an audio signal by performing anoverlap-add process on a group of the frame of input signal of the timedomain transformed in operation 1020. Also, the decoding block 122 maydecode an output audio signal using the original frame of input signal.

FIG. 11 illustrates an example of an audio decoding process according tothe second example embodiment.

The decoding block 122 may decode a 2D inter block 1101 from a bitstreamusing a decoder 1110.

The decoding block 122 may generate frame of input signal 1102 of afrequency domain by dividing the 2D inter block 1101 using a splitter1120.

The decoding block 122 may transform the frame of input signal 1102 ofthe frequency domain to frame of input signal of a time domain. Here,the decoding block 122 may restore groups 1103 of the frame of inputsignal by releasing a window from the frame of input signal of the timedomain. The decoding block 122 may restore an audio signal 1100 thatincludes frame of input signal by performing an overlap-add process onthe groups 1103 using an overlap-addper 1130.

FIG. 12 is a flowchart illustrating a method of encoding an audio signalaccording to a third example embodiment.

In operation 1210, the encoding block 111 may generate a 2D inter blockusing first frame of input signal that constitute an audio signal.

Here, the encoding block 111 may group the plurality of first frame ofinput signal based on an overlap-add. The encoding block 111 may apply awindow to the grouped first frame of input signal. The encoding block111 may transform the first frame of input signal to which the window isapplied to a frequency domain. The encoding block 111 may generate the2D inter block using the first frame of input signal transformed to thefrequency domain.

In operation 1220, the encoding block 111 may encode the 2D inter blockgenerated in operation 1210.

In operation 1230, the encoding block 111 may restore second frame ofinput signal from the 2D inter block encoded in operation 1220. Here,the second frame of input signal may be a result of performing adecoding process on the 2D inter block encoded in operation 1220.

In operation 1240, the encoding block 111 may generate a 2D intra blockusing a residual signal between the second frame of input signalrestored in operation 1230 and the first frame of input signal.

Here, the encoding block 111 may split the residual signal between thesecond frame of input signal and the first frame of input signal into aplurality of subframes. The encoding block 111 may transform thesubframes to a frequency domain. The encoding block 111 may generate a2D intra block using the subframes transformed to the frequency domain.

In operation 1250, the encoding block 111 may encode the 2D intra blockgenerated in operation 1240.

In operation 1260, the encoding block 111 may mix the 2D inter blockencoded in operation 1250 and the 2D intra block encoded in operation1220 and may convert a mixture thereof to a bitstream.

FIG. 13 illustrates an example of an audio encoding process according tothe third example embodiment.

Referring to FIG. 13, an input audio signal 1300 may include a pluralityof first frame of input signal 1301.

The encoding block 111 may group the plurality of first frame of inputsignal 1301 based on an overlap-add. Here, the encoding block 111 mayapply a window to the grouped first frame of input signal. The encodingblock 111 may transform the first frame of input signal to which thewindow is applied to a frequency domain. The encoding block 111 maygenerate a 2D inter block using the first frame of input signaltransformed to the frequency domain.

The encoding block 111 may encode the 2D inter block using an interblock encoder 1310. Here, the inter block encoder 1310 may convert theencoded 2D inter block to an inter block bitstream and may output theconverted inter block bitstream.

The encoding block 111 may restore second frame of input signal from the2D inter block using an inter block combiner 1320. In detail, theencoding block 111 may generate the second frame of input signal byperforming a decoding process of dividing an inter block into aplurality of frame of input signal and by combining the frame of inputsignal.

The encoding block 111 may generate a residual signal 1302 between thesecond frame of input signal and the first frame of input signal using adifferential signal generator 1330.

The encoding block 111 may generate a 2D intra block using the residualsignal 1302. Here, the encoding block 111 may split the residual signalbetween the second frame of input signal and the first frame of inputsignal into a plurality of subframes. The encoding block 111 maytransform the subframes to a frequency domain. The encoding block 111may generate the 2D intra block using the subframes transformed to thefrequency domain.

The encoding block 111 may encode the 2D intra block using an intrablock encoder 1340. Here, the intra block encoder 1340 may convert theencoded 2D intra block to an intra block bitstream and may output theconverted intra block bitstream.

The transmitter 112 may mix the inter block bitstream and the intrablock bitstream into a single bitstream, and may transmit the mixedbitstream to the audio decoding apparatus 120.

FIG. 14 is a flowchart illustrating an audio decoding method accordingto the third example embodiment.

In operation 1410, the decoding block 122 may extract an encoded 2Dinter block and an encoded 2D intra block from a bitstream. The decodingblock 122 may decode a 2D inter block from the encoded 2D inter block.

In operation 1420, the decoding block 122 may restore groups of frame ofinput signal from the 2D inter block decoded in operation 1410. Here,the decoding block 122 may generate frame of input signal of a frequencydomain using the decoded 2D inter block in operation 1420. The decodingblock 122 may transform the frame of input signal of the frequencydomain to frame of input signal of a time domain. Here, the decodingblock 122 may restore groups of frame of input signal by releasing awindow from the frame of input signal of the time domain.

In operation 1430, the decoding block 122 may generate a second frame ofinput signal by performing an overlap-add process on the groups of frameof input signal restored in operation 1420.

In operation 1440, the decoding block 122 may decode a 2D intra blockfrom an encoded 2D intra block.

In operation 1450, the decoding block 122 may restore a residual signalfrom the 2D intra block restored in operation 1440. Here, the decodingblock 122 may generate subframes of the frequency domain using the 2Dintra block. The decoding block 122 may transform subframes of thefrequency domain to subframes of the time domain. The decoding block 122may generate the residual signal by performing an overlap-add process onthe subframes of the time domain.

In operation 1460, the decoding block 122 may restore a first frame ofinput signal that is an original frame of input signal using theresidual signal generated in operation 1450 and the second frame ofinput signal generated in operation 1430. Here, the residual signal maybe a difference between the second frame of input signal that is anframe of input signal restored from the encoded 2D inter block, asgenerated in operation 1240, and the first frame of input signal that isan original frame of input signal.

Accordingly, the decoding block 122 may restore the first frame of inputsignal by adding the residual signal to the second frame of inputsignal.

FIG. 15 illustrates an example of an audio decoding process according tothe third example embodiment.

The decoding block 122 may receive an intra block bitstream convertedfrom an encoded 2D intra block. The decoding block 122 may decode a 2Dinter block from the inter block bitstream using an intra block decoder1510.

Here, the decoding block 122 may restore a residual signal 1501 from the2D intra block decoded in operation 1440.

Also, the decoding block 122 may receive an inter block bitstreamconverted from an encoded 2D inter block. The decoding block 122 maydecode the 2D inter block from the inter block bitstream using an interblock decoder 1530.

The decoding block 122 may restore groups 1502 of an frame of inputsignal from the decoded 2D inter block.

The decoding block 122 may generate a second frame of input signal byperforming an overlap-add process on the groups 1502 of frame of inputsignal.

The decoding block 122 may decode an audio signal 1500 that includesfirst frame of input signal by adding the residual signal 1501 to thesecond frame of input signal using a combiner 1520.

FIG. 16 is a flowchart illustrating a method of encoding an audio signalaccording to a fourth example embodiment.

In operation 1610, the encoding block 111 may generate 2D intra blocksby dividing each of first frame of input signal that constitute an audiosignal into a plurality of first subframes.

In operation 1620, the encoding block 111 may encode the 2D intra blocksgenerated in operation 1610.

Here, the encoding block 111 may set first subframes of the 2D intrablocks to a macro block. The encoding block 111 may predict acorrelation between macro blocks.

The encoding block 111 may perform a DPCM on macro blocks correspondingto a highest predicted correlation. The encoding block 111 may quantizeeach of the macro blocks. The encoding block 111 may calculate aprediction gain based on a result of the DPCM and may quantize aresidual signal between the macro blocks corresponding to the highestcorrelation.

In operation 1630, the encoding block 111 may restore second subframesfrom the 2D intra blocks encoded in operation 1620.

In operation 1640, the encoding block 111 may generate second frame ofinput signal by combining the second subframes restored in operation1630.

In operation 1650, the encoding block 111 may generate residual signalsbetween the second frame of input signal generated in operation 1640 andthe first frame of input signal. The encoding block 111 may generate a2D inter block using the residual signals between the second frame ofinput signal and the first frame of input signal.

In operation 1660, the encoding block 111 may encode the 2D inter blockgenerated in operation 1650.

In operation 1670, the encoding block 111 may output a bitstream inwhich the 2D inter block encoded in operation 1660 and the 2D intrablock encoded in operation 1620 are mixed.

FIG. 17 illustrates an example of an audio encoding process according tothe fourth example embodiment.

The encoding block 111 may generate 2D intra blocks by dividing each offirst frame of input signal that constitute an audio signal 1700 into aplurality of first subframes. The encoding block 111 may encode the 2Dintra blocks using an intra block encoder 1710. Here, the intra blockencoder 1710 may convert the encoded 2D intra blocks to an intra blockbitstream.

The encoding block 111 may restore second subframes from the 2D intrablocks encoded in operation 1620. Here, the encoding block 111 maygenerate second frame of input signal by combining the second subframesusing an intra block combiner 1720.

The encoding block 111 may generate residual signals 1701 between thesecond frame of input signal and the first frame of input signal using aresidual signal generator 1730.

The encoding block 111 may generate groups 1702 by grouping frames thatconstitute the residual signal 1701 by two or more based on anoverlap-add.

The encoding block 111 may generate a 2D inter block using the groups1702.

Here, the encoding block 111 may apply a window to the groups 1702. Theencoding block 111 may transform the groups 1702 to which the window isapplied in operation 720 to a frequency domain. Here, the encoding block111 may transform the frame of input signal to the frequency domain byapplying an MDCT to the groups 1702 based on 50% overlap-add. Theencoding block 111 may generate the 2D inter block using the frame ofinput signal included in the groups 1702 transformed to the frequencydomain. Here, the 2D inter block may be a block that two-dimensionallydisplays frequency coefficients of the frame of input signal transformedto the frequency domain using a time and a frequency.

The encoding block 111 may encode the 2D inter block using an interblock encoder 1740. Here, the inter block encoder 1740 may convert theencoded 2D inter block to an inter block bitstream and may output theconverted inter block bitstream.

The transmitter 112 may mix the inter block bitstream and the intrablock bitstream into a single bitstream, and may transmit the bitstreamto the audio decoding apparatus 120.

FIG. 18 is a flowchart illustrating an audio decoding method accordingto the fourth example embodiment.

In operation 1810, the decoding block 122 may extract an encoded 2Dinter block and an encoded 2D intra block from a bitstream. The decodingblock 122 may decode a 2D inter block from the encoded 2D inter block.

In operation 1820, the decoding block 122 may restore groups of framesof a residual signal from the 2D inter block decoded in operation 1810.Here, the decoding block 122 may generate frames of a frequency domainusing the decoded 2D inter block in operation 1820. The decoding block122 may transform the frames of the frequency domain to frames of a timedomain. Here, the decoding block 122 may restore the groups of theframes that constitute the residual signal by releasing a window fromthe frames of the time domain.

In operation 1830, the decoding block 122 may generate a residual signalby performing an overlap-add process on the groups of the frames of theresidual signal restored in operation 1820.

In operation 1840, the decoding block 122 may decode a 2D intra blockfrom the encoded 2D intra block.

In operation 1850, the decoding block 122 may restore a second frame ofinput signal from the 2D intra block decoded in operation 1840. Here,the decoding block 122 may generate subframes of the frequency domainusing the 2D intra block. The decoding block 122 may transform thesubframes of the frequency domain to subframes of the time domain. Thedecoding block 122 may generate the second frame of input signal byperforming an overlap-add process on the subframes of the time domain.

In operation 1860, the decoding block 122 may restore the first frame ofinput signal that is an original frame of input signal using the secondframe of input signal generated in operation 1850 and the residualsignal generated in operation 1830. Here, the residual signal may be adifference between the second frame of input signal that is an frame ofinput signal restored from the encoded 2D intra block as generated inoperation 1650, and the first frame of input signal that is an originalframe of input signal. Accordingly, the decoding block 122 may restorethe first frame of input signal by adding the residual signal to thesecond frame of input signal.

FIG. 19 illustrates an example of an audio decoding process according tothe fourth example embodiment.

The decoding block 122 may receive an inter block bitstream convertedfrom an encoded 2D inter block. The decoding block 122 may decode agroup 1901 of residual signals from the inter block bitstream using aninter block decoder 1910.

The decoding block 122 may generate a residual signal 1902 that includesframes by performing an overlap-add process on the group 1901 of framesof the residual signal.

Also, the decoding block 122 may receive an intra block bitstreamconverted from an encoded 2D intra block. The decoding block 122 maydecode a 2D inter block from the inter block bitstream using the intrablock decoder 1930.

Here, the decoding block 122 may restore a second frame of input signalusing the 2D intra block decoded in operation 1440. Here, the decodingblock 122 may generate subframes of a frequency domain using the 2Dintra block. The decoding block 122 may transform the subframes of thefrequency domain to subframes of a time domain. The decoding block 122may generate a second frame of input signal by performing an overlap-addprocess on the subframes of the time domain.

The decoding block 122 may decode an audio signal 1900 that includesfirst frame of input signal by adding the residual signal 1902 to thesecond frame of input signal using a combiner 1940.

Here, the second frame of input signal is a result of encoding anddecoding the first frame of input signal. Thus, an audio signal may begenerated using the second frame of input signal only. A signal variesduring an encoding and decoding process. Thus, the second frame of inputsignal may differ from the first frame of input signal that is a frameincluded in an original audio signal. A residual signal refers toinformation indicating a difference between the first frame of inputsignal and the second frame of input signal. Thus, the decoding block122 may enhance the equality of the decoded audio signal 1900 by addingthe residual signal to the second frame of input signal and by decodingthe first frame of input signal.

FIG. 20 is a flowchart illustrating a method of encoding an audio signalaccording to a fifth example embodiment.

In operation 2010, the encoding block 111 may generate 2D intra blocksby dividing each of frame of input signal that constitute an audiosignal into a plurality of subframes.

In operation 2020, the encoding block 111 may encode the 2D intra blocksgenerated in operation 2010.

In operation 2030, the encoding block 111 may generate a 2D inter blockusing residual signals between the 2D intra blocks generated inoperation 2010 and the 2D intra blocks encoded in operation 2020.

In operation 2040, the encoding block 111 may encode the 2D inter blockgenerated in operation 2030.

In operation 2050, the encoding block 111 may mix the 2D inter blockencoded in operation 2040 and the 2D intra block encoded in operation2020.

FIG. 21 illustrates an example of an audio encoding process according tothe fifth example embodiment.

The encoding block 111 may generate 2D intra blocks by applying an intrablock converter 2110 to an audio signal 2100.

In detail, referring to FIG. 21, the intra block converter 21110 maygenerate 2D intra blocks 2101 by dividing each of frame of input signalthat constitute an audio signal into a plurality of subframes and bytransforming the subframes to a frequency domain.

The encoding block 111 may encode 2D intra blocks using an intra blockencoder 2120. Here, the intra block encoder 2120 may convert the encoded2D intra blocks to an intra block bitstream and may output the convertedintra block bitstream.

The encoding block 111 may generate residual signals between the 2Dintra blocks 2101 and the 2D intra blocks encoded by the intra blockencoder 2120.

The encoding block 111 may generate a 2D inter block 2102 by inputtingthe residual signals to an inter block converter 2130.

Here, the encoding block 111 may generate groups by grouping frames thatconstitute the residual signal by two or more based on an overlap-add.The encoding block 111 may apply a window to the groups. The encodingblock 111 may transform the groups to which the window is applied to afrequency domain. The encoding block 111 may generate the 2D inter block2102 using the frame of input signal that are included in the grouptransformed to the frequency domain. Here, the 2D inter block 2102 maybe a block in which the 2D intra block 2101 is represented as afrequency coefficient of a sub-block unit.

The encoding block 111 may encode the 2D inter block 2102 using an interblock encoder 2140. Here, the inter block encoder 2140 may convert theencoded 2D inter block to an inter block bitstream and may output theconverted inter block bitstream.

Here, the transmitter 112 may mix the inter block bitstream and theintra block bitstream into a single bitstream and may transmit thebitstream to the audio decoding apparatus 120.

FIG. 22 illustrates an example of a quantization method according to thefifth example embodiment.

The encoding block 111 may set first subframes of 2D intra blocks to amacro block. The encoding block 111 may predict a correlation betweenmacro blocks.

For example, referring to FIG. 22, the encoding block 111 may predict acorrelation between a macro block 1 corresponding to a first macro blockand other subframes adjacent to the macro block 1. Also, the encodingblock 111 may predict a correlation between a macro block correspondingto a fourth macro block and other subframes adjacent to the macro block4.

Also, as illustrated in FIG. 22, the encoding block 111 may predict acorrelation between a macro block currently being processed and a macroblock that is separate therefrom by a predetermined interval, instead ofusing an adjacent macro block. For example, the encoding block 111 maypredict a correlation between the macro block currently being processedand another macro block that is separate therefrom by a plurality ofmacro blocks. Here, although a probability of retrieving a macro blockhaving an optimal correlation may increase, additional information suchas location information of the other macro block that are separate bythe plurality of macro blocks may be further used. Accordingly, atradeoff may be present between a distance between macro blocks betweenwhich a correlation is to be measured and a probability of retrieving amacro block having an optimal correlation.

The encoding block 111 may perform a DPCM on macro blocks correspondingto a highest predicted correlation. The encoding block 111 may quantizeeach of the macro blocks. The encoding block 111 may calculate aprediction gain based on a result of the DPCM and may quantize aresidual signal between macro blocks corresponding to a highestcorrelation.

FIG. 23 is a flowchart illustrating a method of an audio decoding methodaccording to the fifth example embodiment.

In operation 2310, the decoding block 122 may extract an encoded 2Dinter block and an encoded 2D intra block from a bitstream. The decodingblock 122 may decode a 2D inter block from the encoded 2D inter block.

In operation 2320, the decoding block 122 may restore groups of framesof a residual signal from the 2D inter block decoded in operation 2310.Here, the decoding block 122 may generate frames of a frequency domainusing the decoded 2D inter block in operation 2320. The decoding block122 may transform the frames of the frequency domain to frames of a timedomain. Here, the decoding block 122 may restore groups of frames thatconstitute the residual signal by releasing a window from the frames ofthe time domain.

In operation 2330, the decoding block 122 may restore the residualsignal by performing an overlap-add process on the groups of the framesof the residual signal restored in operation 2320.

In operation 2340, the decoding block 122 may convert an intra blockbitstream to the encoded 2D intra block.

In operation 2350, the decoding block 122 may restore a before-encoding2D intra block using the encoded 2D intra block converted in operation2340 and the residual signal generated in operation 2330. Here, theresidual signal may be a difference between the 2D intra blocksgenerated in operation 2010 as generated in operation 2030 and the 2Dintra blocks encoded in operation 2020. Accordingly, the decoding block122 may restore the before-encoding 2D intra block by adding theresidual signal to the encoded 2D intra block.

In operation 2360, the decoding block 122 may restore an audio signalusing the before-encoding 2D intra block restored in operation 2350. Indetail, the decoding block may restore the audio signal that includesframe of input signal from the 2D intra block by performing operations520 through 540 of FIG. 5.

FIG. 24 illustrates an example of an audio decoding process according tothe fifth example embodiment.

The decoding block 122 may receive an inter block bitstream that isconverted from an encoded 2D inter block. The decoding block 122 maygenerate a residual signal 2401 from the inter block bitstream using aninter block decoder 2410.

In detail, the decoding block 122 may generate frames of a frequencydomain using a decoded 2D inter block. The decoding block 122 maytransform the frames of the frequency domain to frames of a time domain.Here, the decoding block 122 may restore groups of frames thatconstitute a residual signal by releasing a window from the frames ofthe time domain. The decoding block 122 may restore the residual signal2401 by performing an overlap-add process on the groups of the frames ofthe residual signal.

The decoding block 122 may split the residual signal 2401 based on anintra block unit using an inter block splitter 2420.

Also, the decoding block 122 may receive an intra block bitstream thatis converted from an encoded 2D intra block. The decoding block 122 mayconvert the inter block bitstream to the encoded 2D inter block using anintra block decoder 2430.

Here, the decoding block 122 may restore a before-encoding 2D intrablock using the encoded 2D intra block and the residual signals splitbased on the intra block unit. In detail, the decoding block 122 mayrestore a before-encoding 2D intra block 2402 by adding the residualsignal to the encoded 2D intra block.

Here, as illustrated in FIG. 24, the before-encoding 2D intra block 2402may be an intra block that includes a plurality of subframes.

The decoding block 122 may restore an audio signal by combining thebefore-encoding 2D intra blocks 2402 using an intra block combiner 2440.In detail, the decoding block may transform subframes of the frequencydomain included in the 2D intra block 2402 to subframes of a timedomain. Here, the decoding block 122 may restore grouped subframes byreleasing a window from the subframes of the time domain. The decodingblock 122 may decode an audio signal 2400 that includes the frame ofinput signal by performing an overlap-add process on subframes includedin a group and by sequentially determining frame of input signal 1through 12 that constitute the audio signal 2400.

According to example embodiments, it is possible to enhance an encodingefficiency by reconfiguring and encoding an input audio signal as a 2Dsignal. Also, since the same framing structure as a video signal may beachieved using an encoding scheme that is interpreted based on a blockunit, it is possible to flexibly perform homogeneity and synchronizationof an encoding scheme compared to a conventional encoding method.

The methods according to the above-described example embodiments may berecorded in non-transitory computer-readable media including programinstructions to implement various operations of the above-describedexample embodiments. The media may also include, alone or in combinationwith the program instructions, data files, data structures, and thelike. The program instructions recorded on the media may be thosespecially designed and constructed for the purposes of exampleembodiments, or they may be of the kind well-known and available tothose having skill in the computer software arts. Examples ofnon-transitory computer-readable media include magnetic media such ashard disks, floppy disks, and magnetic tape; optical media such asCD-ROM discs and DVDs; magneto-optical media such as floptical discs;and hardware devices that are specially configured to store and performprogram instructions, such as read-only memory (ROM), random accessmemory (RAM), flash memory (e.g., USB flash drives, memory cards, memorysticks, etc.), and the like. Examples of program instructions includeboth machine code, such as produced by a compiler, and files containinghigher level code that may be executed by the computer using aninterpreter. The above-described devices may be configured to act as oneor more software modules in order to perform the operations of theabove-described example embodiments, or vice versa.

A number of example embodiments have been illustrated and describedabove. Nevertheless, it should be understood that various modificationsand alterations may be made to these example embodiments from thedescription.

Therefore, the scope of the disclosure is defined not by the detaileddescription, but by the claims and their equivalents, and all variationswithin the scope of the claims and their equivalents are to be construedas being included in the disclosure.

1. A method of encoding an audio signal, the method comprising: dividingeach of first frame of input signal that constitute an audio signal intoa plurality of first subframes; transforming the first subframes to afrequency domain; determining a two-dimensional (2D) intra block usingthe first subframes transformed to the frequency domain; and encodingthe 2D intra block, wherein the 2D intra block is a block thattwo-dimensionally displays frequency coefficients of the first subframestransformed to the frequency domain using a time and a frequency.
 2. Themethod of claim 1, wherein the transforming of the subframes to thefrequency domain comprises: grouping the first subframes based on anoverlap-add; applying a window to the grouped first subframes; andtransforming the first subframes to which the window is applied to thefrequency domain.
 3. The method of claim 2, wherein the groupingcomprises grouping a last subframe divided from a current frame and afirst subframe divided from a subsequent frame among the first frame ofinput signal.
 4. The method of claim 1, wherein the encoding comprises:dividing each of the first subframes of the 2D intra block into aplurality of subband signals; predicting a correlation between thesubband signals; quantizing a high band signal of which a bandwidthvalue is greater than a reference value among the subband signals, usinga scale factor; quantizing a prediction result of a low band signal ofwhich a bandwidth value is less than or equal to the reference valueamong the subband signals and a residual signal between the subbandsignals; and converting a quantization index, the scale factor, thequantized high band signal, the residual signal, and the predictionresult to a bitstream. 5-19. (canceled)
 20. The method of claim 1,further comprising: restoring second subframes from the encoded 2D intrablocks; determining second frame of input signal by combining the secondsubframes; determining a 2D inter block using residual signals betweenthe second frame of input signal and the first frame of input signal;encoding the 2D inter block; and mixing the encoded 2D inter block andthe encoded 2D intra block.
 21. The method of claim 20, wherein theencoding of the 2D inter block comprises: setting first subframes of the2D intra blocks as a macro block; predicting a correlation between macroblocks; performing a differential pulse code modulation (DPCM) on macroblocks corresponding to a highest predicted correlation; quantizing eachof the macro blocks; and calculating a prediction gain based on a resultof the DPCM, and quantizing a residual signal between the macro blockscorresponding to the highest correlation.
 22. A method of encoding anaudio signal, the method comprising: grouping first frame of inputsignal that constitute an audio signal based on an overlap-add; applyinga window to the grouped first frame of input signal; transforming thefirst frame of input signal to which the window is applied to afrequency domain; determining a two-dimensional (2D) inter block usingthe first frame of input signal transformed to the frequency domain; andencoding the 2D inter block, wherein the 2D inter block is a block thattwo-dimensionally displays frequency coefficients of the first frame ofinput signal transformed to the frequency domain using a time and afrequency.
 23. The method of claim 22, wherein the encoding comprises:dividing each of the frame of input signal of the 2D inter block intosubband signals; predicting a correlation between the subband signals;quantizing each of the subband signals; and calculating a predictiongain based on the correlation and quantizing a residual signal betweenthe subband signals.
 24. The method of claim 23, further comprising:restoring second frame of input signal from the encoded 2D inter block;determining a 2D intra block using a residual signal between the secondframe of input signal and the first frame of input signal; encoding the2D intra block; and mixing the encoded 2D inter block and the encoded 2Dintra block.
 25. The method of claim 24, wherein the determining of the2D inter block comprises: grouping a plurality of first frame of inputsignal based on an overlap-add; applying a window to the grouped firstframe of input signal; transforming the first frame of input signal towhich the window is applied to a frequency domain; and determining a 2Dinter block using the first frame of input signal transformed to thefrequency domain.
 26. The method of claim 24, wherein the determining ofthe 2D intra block comprises: dividing the residual signal between thesecond frame of input signal and the first frame of input signal into aplurality of subframes; transforming the subframes to a frequencydomain; and determining a 2D intra block using the subframes transformedto the frequency domain.
 27. A method of encoding an audio signal, themethod comprising: determining two-dimensional (2D) intra blocks bydividing each of frame of input signal that constitute an audio signalinto a plurality of subframes; determining a 2D inter block usingresidual signals between the 2D intra blocks and encoded 2D intrablocks; encoding the 2D inter block; and mixing the 2D inter block andthe 2D intra block.